Control apparatus for engine starters



y 1, 1952 J. H. BOLLES 2,602,144

CONTROL APPARATUS FOR ENGINE STARTERS Original Filed June 28, 1944 INVENTOR Julius 11301155 HIS ATTORNEYS Patented July 1, 1952 CONTROL APPARATUS FOR ENGINE STARTERS Julius H. Bolles, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Continuation of application Serial No. 542,475,

June 28, 1944. This application September 12, 1947, Serial No. 773,539

8 Claims.

This invention relates to starting apparatus for internal combustion engines, particularly to starting apparatus of the type in which the starter pinion is moved into engagement with the engine gear by an electromagnet, the energization of which is accomplished by the closing of certain manual and automatic switches in a control circuit therefor.

In starting apparatus of this type switches operated by fluid pressure created by the engine, either manifold vacuum or engine oil pressure, have been provided to prevent closing of the control circuit and consequent operation of the starting motor during operation of the engine under its own power. Difliculty has been encountered when such a fluid pressure operated switch is employed to provide. a, switch which will remain open during self-operation of the engine under all operating conditions, but will not open during cranking of the engine by the starting motor. This difficulty arises because the fluid pressure, whether it be manifold vacuum or engine oil pressure, is so low when the engine is operating with wide open throttle under heavy load that such fluid pressure is not greater than would be produced under some conditions when the engine is being rotated by the starting motor. Because of this condition, if the fluid pressureoperated switch is so constructed that it will prevent the closing of the starter circuit when the engine is self-operative under all operating conditions the starter circuit will be opened under some circumstances when the engine is being operated by the starting motor, which is obviously undesirable.

It is, therefore, the primary object of the present invention to provide a starting apparatus of the type referred to which is so constructed that closing of the starter circuit is impossible during self-operation of the engine under any operating conditions and opening of the starter circuit during rotation of the engine by the starting motor is also impossible. 1

According to the present invention the object is attained by the provision of a control circuit for controlling the operation of the main starter switch which includes a fluid pressure switch that is closed when the engine is inoperative and is opened by fluid pressure both when the engine is operated by the starting motor and is self operative, and includes also a bypass circuit around the fluid pressure switch which is open when the engine is inoperative or is operating under its own power, but is closed when the starter switch is closed and the engine is being operated by the starting motor, so that the opening of the fluid pressure operated switch while the engine is being rotated by the starting motor, will not open the starter circuit and cause the starting motor to become inoperative.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of the present invention is clearly shown.

In the drawing: 7

The drawing is a diagrammatic view of a control mechanism for engine starters constructed in accordance with the present invention.

Referring to the drawing, the reference numeral 29 indicates the starting motor which has a ground connection 22 and an armature shaft 24 on which is splined a slidable sleeve 26, which is secured to one member of an overrunning clutch 28, the other member of which'is integral with a driving pinion 30, adapted to be moved into engagement with the flywheel gear 32 of the engine, in order to rotate said gear and start the engine whenever the starting motor is operative. The sleeve 26 is moved to the left, as the device is shown in the drawing, to effect engagement of the pinion 3D with the gear 32 and the circuit between the starting motor and the battery is concurrently closed to cause the starting motor to become operative.

To this end the sleeve 26 is provided with a grooved collar 34, which is slidable on the sleeve 26 and said collar is engaged by pins 36 which project from a yoke formed at the lower end of a lever 38, suitably pivoted at 40 and connected at its upper end with the armature 42 of an electromagnet indicated generally by the reference numeral 44 and which will be more specifically described later. The lever is connected to armature 42 by a pin and slot connection, the purpQSe of which will be described hereinafter, and which comprises the slot 46 in the upper end of the lever and the pin 48 on a link 50 connected to the armature and which projects into said slot.

I When the electromagnet is energized the armature moves to the right, the lever moves collar 34 to the left, the collar pushing against a spring 52 which surrounds the sleeve 26 between the collar and the overrunning clutch previously referred to. The collar is positioned between one end of the spring and a plate 54 secured to the right end of sleeve 26. This movement of the lever pushes the whole sleeve and clutch assembly to the left and if the teeth of the pinion do not abut those of the flywheel, the pinion will be moved immediately into engagement with the flywheel gear. If there is tooth abutment between the pinion and flywheel gear, the spring 52 will be compressed as the lower end of lever 38 moves to the left until the starting motor switch is closed by movement of the armature 42, as more specifically described later. As the switch is closed, the first movement of the motor will move the pinion so that its teeth properly mesh with those of the gear 32, the spring 52 will expand and force the pinion into proper meshing engagement with said gear. This driving mechanism is the same as ordinarily used in manually operated starters of this type, the only change being the substitution of the magnetically operated lever 38 for the usual manually operated foot pedal. A spring 54 returns the lever 38 and associated parts to normal position when the magnet is deenergized.

The starting motor 28 is connected by the wire 56 with a fixed contact 58 of a starting motor switch, while a second fixed contact 62 is connected by a wire 62 with a battery indicated at 64 grounded at 66. A movable contact IE3 is moved into engagement with the two fixed contacts to complete the starting motor circuit when the magnet 44 is energized; such movable contact being supported by a rod I2 which slides in a central aperture in the magnet core I4, and the left end of the rod extends beyond the core to the left so as to be engaged by the armature 62 as it moves to the right upon energization of the magnet. Thearmature pushes the rod to the right and moves contact I2 into engagement with contacts 58 and 6B.

The movable contact 70 is mounted on a block of insulating material I6 which is mounted on the rod I2 between two flanges I8 and 80, which extend from the rod and a spring 82 surrounds the rod between the flange80 and the insulating material I6, such spring tending to hold the block of insulating material against the flange I8 as shown in the drawing. The rod I2 is normally held in the position shown in the drawing with the shoulder 80 bearing against the armature core by the action of a spring 82 which bears against the flange I8 and at the other end against a stationary part which is part of a bracket secured to the magnet housing and has a projection 86 fitting telescopically within a recess or central bore 88 in the rod 72. the magnet is energized, the movement of the armature moves the rod 72 as previously described, and through the actionof the spring 82, yieldingly presses the contact it into engagement with the fixed contacts. Upon deenergizaticn of the magnet, the spring 84 restores the movable contact to the position shown in the drawmg.

When the starter switch has been closed in the manner indicated to complete the starting motor circuit, such motor rotates and the meshing of pinion 32 and gear 32 having been accomplished in the manner described, the motor turns the gear 32 and starts the engine. When the latter is started and is running under its own power, the magnet will be de-energized and the spring 54 returns the parts to the position shown in the drawing, opening the starter switch and disengaging the pinion 33 from the gear 32.

The magnet 44 is provided with two windings 90 and 92, the winding 90 having a ground connection 94, and the winding 92 being connected by a wire 96 with wire 56 which leads from the main starter switch to the starting motor so When 4 that the winding 82 is grounded through the starting motor.

The two coils of the magnet are connected by wires 98 and It?) with a wire I02 which leads to a fixed contact lll of a magnetic switch or relay B having a movable contact I05 which engages the fixed contact when the relay is energized, and is connected by a wire I08 with the battery. Whenever the contacts I04 and IE6 are in engagement, current flows from the grounded battery through wire I08, contacts I04 and I05, wire I62 and wires 98 and I00 to the magnet windings and thence to ground. The magnet is thus energized resulting in operation of its armature to shift the pinion 30 and close the .starter switch, both coils of the magnet being effective until the starter switch is closed. Just as soon as this takes place, the coil 92 is shunted out, so that the switch is held closed during the cranking of the engine only by the effect of the coil 90. This arrangement of the magnet with two coils, one of which is shunted out as soon as the main starter circuit is completed is substantially the same as disclosed in the patent to Dyer No. 2,302,687, November 24, 1942.

The operation of contacts I04 and IE6 to efiect the energization and de-energization of the magnet 42 is effected by a relay B which is controlled by a manually operable switch, a second relay A and a fluid pressure operated switch. The relay B which operates contact I 86 comprises a core H2 and a winding II 2 which, at one end is connected by wire 3' to a fixed contact H4 oi a manually operable switch which includes a-second fixed contact IIG connected by a wire I it to the wire 62 which leads to the battery, and a movable contact I20, normally held open by spring I22, but operable manually to bridge the contacts H4 and H6. The other end of the winding H2 is connected by wire I24 to a movable contact I25, which is normally open, but is movable by a relay, to be described later, into engagement with another fixed contact I28, grounded at I32. Whenever the manually operable switch is closed and contacts I26 and I28 are closed, current flows through the winding I I2 and causes the magnet 44 to be energized. The operation of the contact I26 is so controlled that when the engine is not operating and the manual switch is closed, the contact I26 will be immediately moved into engagement with the contact I28 and it will remain in engagement with the latter as long as the engine is being cranked by the starting motor and the manual switch is held closed, regardless of the effect of the fluid pressure control switch, but if the engine is operating under its own power, it will be impossible to cause engagement of the contacts I25 and I28 upon closing of the manual switch.

To this end the contact I26 is operated by a relay A comprising core I32, and windingifi l, which at one end is connected by a wire I35 to the wire I I3 which leads to the manual switch. The other end of the winding 13 is connected by a wire I38 to anangular supporting member I42 which carries a fixed contact I42 and is supported on a depending U-shaped bracket I42.

The supporting member I46 is held in flxed po sition on the bracket by the screw I56 and separated from the bracket by blocks of insulating material I48.

The bracket i 22 is secured by brazing, or in any other desirable way, to a flange I 59 which projects from a cylinder I52. The latter is provided,

at its upper end, with a peripheral groove in which is secured the lower part I54 of a diaphragm chamber, the upper part of which is indicated at I56. Clamped between the elements I54 and I56 is a diaphragm I58, and the upper part I56 of the diaphragm chamber is bent over at the periphery as indicated at I60, to clamp between this bent over portion and the portion I56, the lower part I54 and the diaphragm, so as to form a fluid-tight joint. A threaded nipple I62 is secured as shown at the center of the part I56, and a conduit I64 is provided and may be connected with the oil line of the engine, if oil pressure is employed, or with the manifold if suction is employed to operate the diaphragm. This conduit is screwed into such nipple, so as to convey oil under pressure to the diaphragm, or to communicate engine suction thereto. If suction is employed, the conduit should be connected below the diaphragm.

A rod I66 is connected in any suitable way to the center of the diaphragm and extends downwardly therefrom through the cylinder I52. At its lower end, the rod is reduced in size as indicated at I68 and surrounding this part of the rod is a washer I and a flanged collar I12 of insulating material. Received around the cylindrical part of the collar and between the washer I10 and the flange which projects from the collar is a spring I14, supporting a movable contact I16 which is adapted to engage the'fixed contact I42 when the engine is not in operation. The reduced part I68 of the rod I66 is riveted over the flanged collar, as shown in the drawing, to hold the collar in position. 'The cylinder I52 is closed at its lower end except for an orifice in which the rod I66 fits loosely, and a spring I18 is positioned in said cylinder around the rod, between the closed lower end of the cylinder and the diaphragm I58, such spring acting to hold the diaphragm in the position with the switch contacts I42 and I16 in engagement when the engine is inoperative. The spring I14 is connected, as indicated in the drawing, by awire I80 which extends from the spring to one of the-brushes of the generator I82 which is grounded as indicated at I84. Therefore, the spring I14 is grounded through the generator and the connection I84. The generator is connected by the wire I86 to the battery to effect charging thereof and the usual cut-out relay I88 is provided in this connection. The generator and the connection therefrom to the battery is of conventional construction and need not be further described.

It will be understood that if the spring I14 isv grounded through the generator, as described, the main magnet may be rendered inoperative by the generator whenthe latter reaches a predetermined speed and under certain operating conditions, for reasons which will'be more fully set forth in the description of the operation of the device that appears hereinafter.

Attention is called to the fact that the sprin I14 may have a ground connection leading directly from the spring to ground without passing through the generator. As willbe apparent from the description of the operation which follows later on, if the device is constructed in this way, the starting motor will always continue to operate until the manually operable push button 220 is released, whereas if grounded through the generator, as illustrated in the drawing, the starting motor, under certain circumstances, may be rendered inoperative by the generator as soon as the engine begins to run under its own power and operates rapidly enough to bring the speed of the generator up to the point required to cause the de-energization of the main magnet. Likewise, if the generator ground connection is used as shown, the generator will prevent any possibility of accidental operation of the starting motor during self-operation of the engine, even in the event of failure of the fluid pressure switch.

For a purpose to be more fully explained, there is a second ground connection for the winding I34, when the contacts I26 and I28 are closed.

' To this end a wire I90 is connected to the winding I34 and is also connected to the switch contact I26.

It will be understood that instead of connect ing the upper half of the diaphragm with a source of oil under pressure to effect opening of the contacts I42 and I16, when the engine is in operation, the upper part of the diaphragm chamber could be made solid except for a vent and a suction conduit could be connected to the lower part of the diaphragm chamber and the intake manifold so as to communicate the engine suction to the lower side of the diaphragm to pull the diaphragm down when the engine is running.

From the foregoing description, it will be apparent that the normal position of the parts, that is, the position of such parts when the engine is inoperative is as shown in the drawing, with the pressure operated switch closed. If the manually operated switch button 220 is then operated to close the switch operated thereby, current will first flow from the battery through such switch, the wire II3, wire I 36, winding I34, wire I33, contacts I42, I16, spring I14 and connection I80 through the generator to ground. This will energize relay A and efiect closing of contacts I26 and I28. Closing of these contacts will immediately cause the energization of relay B because current flows from the battery, through the manual switch, winding I42, wire I24 and contacts I26, I28 to ground. As soon as relay B is energized, the main magnet 44 is energized, the main starter circuit is closed and the pinion 30 is moved into mesh with the gear 32 as previously described. The engine will then be cranked and ultimately will be started.

During thecranking of the engine, fluid pressure, either the oil pressure or manifold vacuum, whichever is used, may be effective to move the diaphragm down against the force of springs I14 and I18. Under some conditions, the force exerted by this fluid pressure is great enough,

even during the cranking period and before the engine begins to operate under its own power, to cause separation of contacts I42 and I16, but with the device disclosed, this cannot cause the deenergization of the main magnet 44, nor cause the starting motor to become inoperative, unless the operator, himself, opens the manually operated switch. Operation of the generatormay cause the de-energization of the main magnet under certain circumstances, but never during cranking, as the generator speed is insufficient. 7

Because of the second ground connection for the relay A, comprising wire I90, contacts I26, I28 and ground connection I30, which is established when relay A is energized, the opening of the ground connection for such relay which includes the fluid pressure switch, does not have any de-energizing efiect on the relay. In other words, after initial energization of relay A, to cause operation of the starting motor, the relay cannot generally be de-energized except by deliberate action of the operator, in opening the manual switch.

On the other hand, if the engine is operating under its own power, neither the relay A nor the main magnet will be energized, even if the fluid pressure falls so low that the fluid pressure switch is closed, so that the starting motor cannot be caused to become operative. Even if the fluid pressure became so low that the switch operated thereby were closed, the generator would be op crating rapidly enough to de-energize the winding I34 and the closing of the manually operated switch would have no effect.

Ordinarily the generator has no effect in causing de-energization of the main magnet, but is effective in the event of failure of the fluid pressure switch or great delay in the operation of such switch, to bring about the de-energization of the main magnet when the engine operates under its own power and fast enough to drive the generator at more than a predetermined speed.

If at any time when the generator is operating at a speed above the predetermined speed referred to and the fluid pressure switch is closed, current will flow from the generator through wire I86, the fluid pressure switch and wire I38 to the winding I 34 through which it flows in a direction opposite to the current flowing from the battery. This nullifies the action of the battery current on said winding and causes contacts I26 and IE8 to separate, which results in the de-energizing of the magnet for reasons that will be apparent. Whenever the fluid pressure switch is open, current from the generator can not flow to the winding I34, so that the generator has no tie-energizing function at any time that said fluid pressure switch is open. Since the fluid pressure switch is opened under normal circumstances during engine cranking and before the generator is operated at sufficient speed to have any eflect, the main magnet is de-energized, under normal con ditions only by opening of the manual switch.

However, if there should be any failure of the fluid pressure switch due to a broken diaphragm, or for any other reason, or if there is sufiicient delay in the operation of the fluid pressure switch, due to oil viscosity or any other cause, which is sufficient to enable the generator to attain the necessary speed of operation before the opening of the fluid pressure switch, the action of the generator will de-energize the main magnet.

Likewise the generator will prevent any energization of the main magnet during self-operation of the engine if the manual switch be accidentally closed. In the event of failure of the fluid pressure switch, or if the speed of the engine would be reduced sufficiently to enable the closing of the fluid pressure switch, operation of the manual switch would not cause the main magnet-to be energized because as soon as the fluid pressure switch closed, the generator would de-energize winding I34 and closing of the manual switch would not effect closing of contacts I26 and 528.

Normally, when the engine starts to operate under its own power, the fluid pressure separates the contacts I42 and I15 and the operator releases the manual switch. The opening of the fluid pressure switch breaks one ground connection of the relay A and the opening of the manual switch breaks the other ground connection of such relay, comprising contacts I26 and I23.

Under normal conditions, the fluid pressure switch remains open as long as the engine is self operative and accidental closing of the manual switch will have no effect. Under abnormal conditions such as previously referred to, the action of the generator will efiect opening of the contacts I26 and I28 when the fluid pressure switch fails to remain open, whenever the engine is selfoperative, so that accidental operation of the manual switch cannot cause the main magnet to operate as long as the engine is self-operative, regardless of what may happen to the fluid pressure switch, or how long a delay there may be in the action of the fluid pressure switch.

As already stated in the foregoing description, the fluid pressure switch which is operable by the engine may be operated by either oil pressure or'by the engine suction or manifold vacuum.

The oil pressure operated switch has one advantage which may be mentioned. Sometimes in starting an engine the engine will make two or three rotations and then stop. Due to the inertia of the parts, they will remain in motion for a brief period of time and if the pressure operated switch could close during such period of time, it might result in the starting motor being rendered effective because the manually operated switch would be still closed by the operator. This would result in damage to the starter pinion and flywheel gear so that it is desirable to prevent any possible reclosing of the pressure operated switch under such conditions. When oil pressure is employed there is a definite lag in the operation of the switch due to the viscosity of the oil, particularly in cold weather. This delay will cover a period of several seconds and is sufficient to assure that the engine parts are fully stopped before the reclosing of the switch can take place.

This application is a continuation of application Serial No. 542,475, filed June 28, 1944, which application has now become abandoned.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within' the scope of the claims which follow.

What is claimed is as follows:

1. Starting apparatus for internal combustion engines comprising, in combination, a current source, a starting motor operable by current from said source, a main switch for connecting the starting motor and current source, a magnet for operating said main switch, a control circuit for controlling the action of said. magnet and including a control switch operated by fluid pressure created by the engine and operable to prevent energization of said magnet during self operation of the'engine, said switch being opened by said pressure both when the engine is selfoperative and when rotated by the starting motor and the control circuit being 50' arranged that the fluid pressure switch must be closed to effect initial closing of the main switch, a second switch in circuit with the fluid pressure switch and eifective upon closing to bring about a closing of the main switch if the fluid pressure switch is also closed, a third control switch the closing of which is effected upon closing of the control circuit and which is effective when closed to establish a second control circuit for said magnet by-passing said fluid pressure switch so that when said fluid pressure switch is opened as the engine is rotated by the starting motor, the magnet will not be deenergized to render the starting motor inoperative as long as said third switch remains closed.

2. Starting apparatus for internal combustion engines comprising, in combination, a current source, a starting motor operable by current from said source, a main switch for connecting the starting motor and current source, a control ciris self-operative. and during cranking, said control circuit being so arranged that both the manual and pressure operated switches must be closed to effect closing of the main switch, means rendered effective by closingof said control circuit to establish a second control circuit bypassing the fluid-pressure switch, whereby when the latter is opened during engine cranking the main switch remains closed, means whereby the open ing of the manual switch when the engine becomes self operative will cause the opening of the second control circuit, a generator, and means operable by the generator to prevent closing of the second control circuit during self-operation of the engine if the fluid pressure switch fails to open.

3. Engine starting apparatus for internal combustion :engines comprising, in combination, a current source, a starting motor operable by current from said source, a main magnetic switch for connecting the starting motor with the current source, a control circuit for controlling the operation of said magnetic switch which includes a first control switch, operable by fluid pressure created by the engine andopened by such pressure when the engine is self-operative to prevent closing of the main switch, or when operated by the starting motor, said control circuit also including a second control switch in series with the fluid pressure switch and so arranged that both said switches must be closed to effect the initial closing of the main switch, a third control switch which is closed by the closing of said control circuit and when closed is effective to maintain the main switch closed irrespective of the condition of the fluid pressure switch whereby when the fluid pressure switch is opened during operation of the engine by the starting motor, the main switch will remain closed.

4. Engine starting apparatus for internal combustion engines comprising, in combination, a current source, a starting motor operable by cur rent from said source, a main magnetic switch for connecting the starting motor with the current source, a control circuit for controlling the operation of said magnetic switch which includes a first control switch, operable by fluid pressure created by the engine and opened by such pressure when the engine is self-operative to prevent closing of the main switch or when operated by the starting motor, said control circuit also including a second control switch in series withv the fluid pressure switch and so arranged that both said switches must be closed to effect the initial closing of the main switch, a third control switch which is closed by the closing of said control circuit and when closed is effective to maintain the main switch closed irrespective of the condition of the fluid pressure switch whereby when the fluid pressure switch is opened during operation of the engine by the starting motor, the main switch will remain closed, a generator and means operable by the generator to prevent closing of the main switch during self-operation of the engine if the fluid pressure switch fails to open.

5. Engine starting apparatus for internal combustion engines comprising, in combination, a

current source, a startingmotor operable by current from said source, a main magnetic switch for connecting the starting motor with the current source, a control circuit for controlling the operation of said magnetic switch which includes a normally closed control switch operable by fluid pressure created by the engine and opened thereby when the engine is self-operative to prevent closing of the main switch and also opened when the engine is being operated by the starting motor, said control circuit being so arranged that said fluid pressure switch must be closed to effect initial closing of the main switch, a second normally open switch in said control circuit in series with said fluid pressureswitch and effective upon closing to cause the closing of the main switch, and a third normally open control switch the closing of which is effected by said second control switch and which is efiective when closed to maintain the main switch closedirrespective or the condition of the fluid pressure switch, whereby when the latter is opened during operation of the engine by the starting motor, it does not efiect opening of the main switch.

6. Engine starting apparatus for internal combustion engines comprising, in combination, a current source, a starting motor adapted to be operated by current from said source, a main switch for controlling the circuit between the current source and starting motor, a control circuit for controlling the operation of the main switch which includes a control switch operated by fluid pressure and so constructed that the pressure created by the engine, either when operated by the starting motor or when self-operative, may be efl'ective to open the switch, a second control switch that when closed maintains the main switch in closed condition and is closed at the same time the main switch is closed and independently of the operation of the starting motor, whereby the main switch is held closed during operation of the engine by the starting motor regardless of the condition of the pressure operated switch, a generator and means whereby under certain operating conditions, the generator is effective when the engine becomes self-operative to effect opening of said second control switch.

'7. Starting apparatus for internal combustion engines comprising, in combination, a current source, a starting motor operable by current from said source, a main starter switch adapted to close the circuit between said current source and the starting motor, a magnetic switch between the current source and the main switch operable to effect closing of the main switch when it is closed, a control circuit for the magnetic switch which includes a control switch operable by fluid pressure created by the engine and in circuit with the winding of said magnetic switch, said control switch being normally closed and so constructed that it may be opened during selfoperation of the engine or when said engine is being operated by the starting motor, a second magnetic switch in circuit with the winding of the first magnetic switch and having a winding in circuit with the fluid pressure operated switch, said second magnetic switch being so constructed that when closed it establishes a ground connection for its own winding and for that of the first magnetic switch, and means for causing the closing of the second magnetic switch when the first magnetic switch is closed to cause operation of the starting motor and for maintaining said second magnetic switch closed while the engine is being operated. by said starting motor, whereby the fluid pressure switch may open without causing the starting motor to become inoperative.

'8. Starting apparatus for internal combustion engines comprising, in combination, a current source, a starting motor operable by current from said source, a main starter switch adapted to close the circuit between said current source and the starting motor, a magnetic switch between the current source and the main switch operable to effect closing of the main switch when it is closed, a control circuit for the magnetic switch which includes a control switch operable by fluid pressure created by the engine and in circuit with the winding of said magnetic switch, said control switch being normally closed and so constructed that it may be opened during self-operation of the engine or when said engine is being operated by the starting motor, a second magnetic switch in circuit with the winding of the first magnetic switch and having a winding in circuit with the fluid pressure operated switch, said second magnetic switch being so constructed that when closed it establishes a ground connection for it sown winding and for that of the first magnetic switch, means for causing the closing of the second magnetic switch when the first magnetic switch is closed to cause operation of the starting motor and for maintaining said second magnetic switch closed while the engine is being operated by said starting motor, whereby the fluid pressure switch may open without causing the starting motor to become inoperative, a generator and a connection from said generator to the winding of the second magnetic switch so that under certain operating conditions the generator is efiective to prevent closing of said second magnetic switch when the engine is operating under its own power.

JULIUS BOLLES'.

REFERENCES, CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,908,088 Warner May 9, 1933 1,981,879 Sayre Nov. 27, 1934 1,981,880 Sayre Nov. 27, 1934 2,078,608 Maurer Apr. 27, 1937 2,105,723 Dyer et a1. Jan. 18, 1938 

